A known solenoid valve is of a type comprising a magnetic head, a valve body and a chamber, whose upper boundary on the side of the magnetic head which is remote from the valve body is provided with a magnet core and in which an armature movable against a spring force and carrying a sealing pin with a sealing face for closing a passage is arranged.
The armature, to whose lower end the sealing pin is fitted, is pressed downwards against the valve body by the force of the spring, so that the sealing face of the sealing pin is firmly pressed against the passage orifice, thus closing the passage. In order to open the valve, the magnetic head is energised, creating a magnetic field in which the armature is pulled up towards the core against the spring force. In this way, the sealing face of the sealing pin is lifted off the orifice of the passage, allowing the medium to flow through.
The disadvantage of this solenoid valve lies in the fact that the armature can only be actuated in one direction by way of the magnetic field and that another solenoid valve is required for applications in which the sealing pin is supposed to be lifted off the orifice by the spring when no voltage is being applied, while being pressed against the orifice to close the valve as soon as the magnetic field is switched on. This arrangement necessitates extensive spares storage, since different solenoid valves are required for the opposing control functions, and if the direction of control is reversed as a result of subsequent changes in operating methods, a completely new valve has to be installed.
The present invention is aimed at obviating or mitigating the disadvantages outlined above and at creating a solenoid valve of the type described, which can be adapted to perform closing and opening functions in opposite directions without requiring additional control components.
According to the present invention there is provided a solenoid valve comprising a valve body and a magnetic head, a chamber arranged within the confines of the magnetic head and having a pair of opposite sides defined by respective magnet cores, an armature movable in the chamber and mounting a sealing member with a pair of opposed sealing faces for closing a communication between the chamber and respective passages, and means biassing the armature in one direction of movement towards one of the magnet cores, a spacing between the armature and the other of the magnet cores being less than the spacing between the armature and said one magnet core. PG,4
This arrangement offers the advantage of alternative options, since the solenoid valve may either be operated in a "de-energised closed" mode or else in a "de-energised open" mode. When operating in the "de-energised closed" mode, the sealing face of the sealing pin is firmly pressed against the orifice of the passage in the lower magnet core by spring action. As the distance between the armature and the upper magnet core remote from the orifice is shorter than the distance between the armature and the second, lower magnet core, the armature is pulled upwards against the force of the spring, as soon as the current flows across the magnetic field, thus lifting the sealing pin and opening the passage. For applications in the "de-energised open" mode, the control assembly consisting of armature, sealing pin and spring is simply turned by 180.degree. within the chamber, so that the other sealing face of the sealing pin is now facing the passage orifice and the sealing pin is lifted off the orifice by the spring. In this case, the armature is closer to the lower, second magnet core than to the opposing upper magnet core. When current is introduced, the armature is pulled towards the lower magnet core against spring action by the magnetic field, firmly pressing the sealing pin against the passage orifice in order to check the flow of the medium. In this way, the control mode can be reversed in an extremely simple way without involving any additional components, thus permitting a significantly smaller quantity of parts to be stocked and the solenoid valve to be adapted to subsequent changes in operating methods.
In order to eliminate the possibility of the magnetic force being adversely affected in the larger air space as a result of air gap induction on that side of the armature which faces the associated magnet core across the larger distance, which might make it impossible to ensure a perfect control function in certain cases involving extremely high efficiency requirements, a preferred embodiment of the invention provides for a short-circuit section which connects the armature to the more distant magnet core. This arrangement offers the advantage of magnetically short-circuiting the air gap between armature and magnet core. This magnetic short-circuit virtually reduces induction on this side of the armature to zero, so that there is no development of magnetic force. When the magnetic head is energised, the buildup of magnetic induction is therefore limited to the other side of the armature, which, unaffected by opposing magnetic forces, is able to function efficiently, and the armature is pulled powerfully in one direction only towards the core concerned. This provides for high efficiency and ensures reliable functioning even in operating conditions which require a very high performance.